Master key for cylinder locks



Nov.,25, 1930. 1 M, F LK 1,782,464

MASTER K EY FOR CYLINDER LOCKS Filed May 18, 1928 I, III/III A ll/IIlI/llllllfl Patented Nov. 25, 1930 UNITED STATES MORRIS FALk, OF FITCHBURG, MASSACHUSETTS MASTER KEY FOR CYLINDER LOCKS Application fiied may 18,

This invention has relation to cylinder locks, and in particular to the master keys commonly provided to fit a plurality of such locks when the latter are associated in a systom. Such association of a great number of difierent locks, each intended to be opened by its individual and respective key or keys, is of common occurrence in present practice, an instance being the installation of one or more looks in connection with each vehicle produced by an individual automobile manufacturing concern, and applied to the doors, transmission, ignition, tire-carrier, etc., of such vehicle, to prevent unauthorized use of the vehicle and itsaccessories.

' Need frequently arises for operating such locks in the absence of the proper and in,- tended keys therefor, as in case of loss of said keys";- and inasmuch as the provision of master keys to fit a series of locks numbering into the thousands has hitherto been possible in practicable manner only through predetermined and relatively costly structural de-. partures from the common construction of the locks themselves, such provision has been omitted on the basis of unwarranted expense.

Instead, it has been the usual practice in the past to stamp the serial number of each lock upon the front of the cylinder thereof, and to put into the hands of locksmiths and the agents of the automobile manufacturing concern such information as to'the construction or combination of the lock as would enable them tQ supply a key therefor when given its serial number. -However, with the discontinuance of this numbering practice by automobile manufacturers, the loss of the proper keys by the car-owner has usually necessitated the destruction of the look by drilling or breaking it out of its place, with attendant expense and loss of time.

The object of the present invention is to provide a master keysystem adapted to operate cylinder locks which have not been structurally designed to be opened by master keys, in order to save loss of time and effort, and destruction and subsequent replacement of locks or their associated structures when the proper keys have been lost.

An illustrative embodiment of the inven- 1928. Serial no. 278,901.

tion is shown in in which i Fig. 1 shows in profile view a master key einbodyin the invention, showing the five notches 0 s ecial depth adapted to operate 'pylinder 100 of the common five-tumbler Fig. 2 shows in profile view a common key designed to fit a single five-tumbler cylinder I lock showing the relative depth of each of the live standard depths of notches;

Fig. 3 is a view in vertical section lengthwise of a standard five-tumbler cylinder'lock, showing the proper key in place and the parts in unlocked relation; 1

Figs. 4, 5 and 6 show transverse sectional views of several difierent key-ways, as formed in the cylinders of difi'erent locks;

Fig. 7 shows in profile view a master key designed'to enter all of the key-ways of Figs. 4, 5 and 6; Y

Fig-8 is a transverse section of the master key shown in Fig. 7 and ig. 9 is'a view similar to Fig. 3 showing the invention applied to a lock of the disc type. t t t a A typical five-tumbler rotatable cylinder look, as shown in section in Fig. 3, comprises a body 1 adapted to be secured to a door or other part, and a cylinder 2 fitting closely therein, with capacity for rotation upon its axis within the body 1. This cylinder 2 familiarly has a finger 3 fixed upon its inner end for efl'ecting the actual lockin either itself or through actuating a door latch or the like,.when the cylinder 2 is turned. To prevent rotation of the cylinder 2 except when the proper key is inserted in the keyway 5 therein, tumblers or pins 4, 4, are fitted into radialholes formed in a line in the plane of the key-way, and similar pins 6, 6, pressed toward the cylinder by lightsprings 7, 7, are fitted into holes in the body 1 which ali exactly with those of the cylinder 2 when t e cylinder is turned to the proper point. The cylinder is free to turn only when the pins 4 and 6 are. thrust outward sufliciently to bring the outer ends of the pins 4, 4,,mounted the accompanying drawings,

y in the cylinder, just flush with the surface of the cylinder. If one of these pins 4 is not thrust outward far enough, the co-acting pin 6 will extend inward into the hole in the cylinder aligned with it and occupied by its coacting pin, and prevent relative rotation of the cylinder, while if one such pin 4 is thrust outward too far it will enter the hole in the body 1 occupied by its co-acting pin 6, likewise to prevent rotation of the cylinder. \Vhen the key is withdrawn, the pins (3. 6, enter the holes in the cylinder and prevent rotation.

The upper edge of the proper key S to tit this lock is formed with the familiar notches or cuts for the purpose of lifting the pins 4, 4, to the proper extent to bring their upper ends flush with the surface of the cylinder 2, and permit rotation of the cylinder.

The pins 4, 4, are of different lengths, varying from each other by an arbitrary increment which is chosen by the lockmaker and thereafter adhered to throughout the production of an entire series of locks. Consequently, the notches in the keys for these locks vary from each other in their depth, measured from the original straight edge of the key blank, by an increment which remains standard for the entire series.

These notches, each differing in depth from the other by a standard amount in a certain series, are given numbers which are used to indicate to the proper persons informed of this standard difference, the combination of the lock. Thus, if the pin nearest the point of the inserted key is leveled with the cylinder by the uncut top edge of the blank key, the designation is a No. 1 notch, which in reality is no notch at all, (Fig. 1). If the second pin from the point is longer than the first by the standard increment, the notch cut therefor in the key will be described as a No. 2 notch, and so on, a No. 5 notch being of a depth four times the standard increment.

I have discovered that a key will still operate to work a lock notwithstanding a variation between the depth of its notches and the standard depths of similar notches in the proper key made for that lock, provided this variation or difference does not exceed a certain amount. I have observed that this allowable variation from the standard depths is in excess of one-half the, linear value of the standard increment used by lockmakers. Consequently, by making a given notch on my novel key of a depth intermediate the standard notch of a certain depth and the standard notch next deeper in that lookmakers system, that is, using a depth of notch which bears a fractional relation to the standard increment, my key will be enabled to work two locks, each intended to respond only to its proper key, and with a variation between them of the full standard increment as regards the given notch. To put it otherwise, if one lock has a pin nearest the point of the inserted key which will be leveled by a No.3 notch, and another lock, otherwise similar, has a correspondingly located pin lev eled by a No. l notch, my novel key having a notch in that position of a depth of 2 standard increments, or what might be called a No. 3 notch, will level such pin in either lock closely enough to permit the cylinder to be turned and the lock opened.

It now each of the five cuts or notches on my improved key needed to control the lifting of the pins in a common five-tumbler cylinder lock be made of this novel intermediate depth, say all be made No. 3 notches, each cut or notch will adequately level a pin designed to be leveled by either a No. 3 or No. l notch on its proper key. Hence a master key thus cut will work such a lock having its pins made all for No. 3 notches iu its proper key, or all No. 1 notches, or

having any and every combination of No. 3-

and No. l notches. or a total of 31 different locks. Similarly. I make master keys having all five notches No. 1 No. 2 and No. 4 amlcontinue to make them in every possible combination of these intermediate depths, and in every possible order, until I have completed the entire range of 234 possible combinations. Since the total number of possible combinations of notches in any one system of five-tumbler cylinder locks is 7 .254; looks, I am able to provide a set of 234 master keys operating on the principle of my invention and containing in each set some one key that will open a given lock in the system.

To increase the number of total combinations possible, it has been the usual practice to employ a key-way of irregular section having protrusions or inwardly projecting ribs such as 9, and to form appropriate grooves in the key blank so as to let only a suitably grooved key into the lock. Examples of the different shapes of key-Way are shown in Figs. 4, 5 and 6, through the use of which three shapes the total number of possible combinations stated above may be trebled, to give a total of 21,762 lock changes in this instance.

To permit the use of this familiar principle of grooving in connection with my master keys, I have devised a special form of groovmg shown in Fig. 8 which will enter all of the three key-Ways shown in Figs. 4, 5 and 6, the groove 10 being wide enough to accommodate either the angular rib 11, or the reversed rib 12, or the two ribs 13, 14, shown in Fig. 4. Thus each of my master keys working 31 tumbler combinations as aforesaid will be able to enter each of these three key-ways, and hence can open 93 different locks, and the set of 234 master keys will serve for 21,7 62' locks. The forms of key-ways shown are only examples, and not restrictive. Many other difierent forms of key-ways may be chosen into which a master key thus formed as indicated in Fig. 5 with one or more wide grooves'will enter, while the proper key for one form will be excluded from all the others.

I have described the invention above as applied to a pin tumbler cylinder look, but it is equally applicable to a disc type look as shown in'Fig. 9. In this figure the same reference numerals are used to designate corresponding parts. 7

, Through the temple ment of my invention,

10 it become possible to strike the proper combination of a lock for which the proper keys are missing, out of a total of 234 tries, a process taking at the outside only ten to fifteen minutes; it then becomes a simple matter to'make a duplicate of the key that has opened the lock; the lock is kept is service, saving the labor and expense of destruction and replacement, loss of time, or the effort involved in trying to find the right combination out of 21,762 or more possibilities Sets of my improved master keys appropriate to the lock system of an automobile manufacturers product can be distributed to the authorized representatives thereof at various points, to be quickly'available to proper persons in emergencies arising through the loss of a car-owner s keys.

I am aware that various modifications, extensions and alternative embodiments of the principles of my invention may be made by a person killed in the art, without departing from the scope of my invention.

What I claim as m invention, and desire to secure by Letters atent is 1. In a locksystem employing keys having notches or cuts varying from each other in depth by a standard increment, a master key therefor having its notches or cuts of a v depth bearing a fractional relation to said standard increment.

- 2. A master key having notches or cuts of a depth intermediate the standard notch of a certain depth and the standard notch next deeper in a given system of locks.

In testimony whereof I have hereunto affixed my signature.

, t MORRIS FALK. 

